The Pacitan Regency is at risk of megathrust earthquakes and tsunamis due to the seismic gap along the southern region of Java Island, making risk-reduction efforts crucial. This research aims to analyse the tsunami risk associated with a potential megathrust earthquake scenario in Pacitan’s coastal areas and develop sustainable mitigation strategies. The research employs spatial analysis to evaluate the risk and subsequently formulate strategies for long-term mitigation. A weighted overlay method was utilised to integrate hazard (H) and vulnerability (V) datasets to produce a tsunami risk map (R). The hazard component was modelled using a tsunami propagation simulation based on the Shallow Water Equations in the Delft3D-Flow software, incorporating an earthquake scenario of Mw 8.8 and H-loss calculations in ArcGIS Pro 10.3. The vulnerability assessment was conducted by overlaying population density, land use, and building footprint from the Global Human Settlement Layer (GHSL) datasets. Finally, sustainable strategies were proposed to mitigate the tsunami risk effectively. The results show that Pacitan faces significant tsunami disaster risk, with tsunami waves at the coast reaching 16.6 m. Because the coast of Pacitan is densely populated, mitigation strategies are necessary, and in the present contribution, the authors developed holistic spatial planning, which prioritise the preservation and restoration of natural barriers, such as mangroves and coastal forests.

Small coastal peat islands such as Bengkalis (Riau, Indonesia) are hydrologically sensitive systems where groundwater level (GWL) controls ecosystem stability. Both extremes are hazardous: prolonged low GWL elevates peat-fire, subsidence, and carbon-loss risks, while excessively high GWL can trigger bog-burst. This study developed a simple empirical model to predict daily GWL in degraded peatlands on Bengkalis Island using in situ GWL data from three sites (drained, undrained inland, and undrained coastal) and GPM satellite rainfall (October 2023-April 2025). Calibrated over one year and validated over the next seven months, the model performed well at drained and coastal sites (R ~0.82, MAPE ~14%), capturing seasonal dynamics. In contrast, its performance at the inland site was lower (R ~0.5) due to minimal water table fluctuation. Coefficient values indicate the strongest rainfall response and fastest losses at the drained site, negligible daily loss at the inland site, and intermediate behavior at the coastal site. Scenario simulations highlight management-relevant risks: 15 rain-free days cause GWL to drop below the critical -0.40 m fire-risk threshold at the drained site and coastal site, whereas undrained inland remains just above it; conversely, 60 mm/day of rain for four days can raise GWL to the surface at coastal site (bog-burst risk). The model provides a practical tool for informing rewetting strategies to manage fire and collapse risks in degraded tropical peatlands.